SSAWG Ray Weil and Joel Gruver

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Cultivating curiosity pride of
understanding
and
Joel Gruver
Interview Seminar 4/14/06
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Teaching Experience
Central Carolina Community College
Principia College
Tufts University
Center for Environmental Farming Systems
University of Maryland
NCSU Soil Science
Hampshire College
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The Hidden Half of Agriculture
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Major soil resource areas in Illinois
Topography of McDonough County, IL
Soil Associations in McDonough County, IL
Southern Wisconsin and Northern Illinois Drift
Plain Southern Michigan and Northern Indiana
Drift Plain Northern Mississippi Valley Loess
Hills Illinois and Iowa Deep Loess and
Drift Northern Illinois and Indiana Heavy Till
Plain Central Claypan Area Southern Illinois
and Indiana Thin Loess and Till Plain Central
Mississippi Valley Wooded Slopes Kentucky and
Indiana Sandstone and Shale Hills and
Valleys Southern Mississippi Valley
Alluvium Southern Mississippi Valley Silty
Uplands
Can anyone name this soil ?
Soil Survey map 29 McDonough County, IL 1 12,000
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Sable silty clay loam
Fine-silty, mixed, superactive, mesic Typic
Endoaquoll
600,000 acres mapped in Illinois, Indiana and Iowa
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Bacteria
A worms eye view
A nematodes eye view
Soil is habitat !
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Tortuous, loosely connected and highly
constricted porosity
Structural rigidity
Soil presents its inhabitants with many challenges
Low quality nutritional resources
Moisture fluctuations
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As a result, most soil microorganisms are in a
dormant state
For their prince charmings to arrive !
waiting
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Roots
Rain
There are many types of prince charmings !
Tillage
Organic Amendments
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Cutting
Crushing
Milling
Beating
Rebound
What is tillage ?

Mechanical modification of soil structure
Tool action tilth soil dynamics
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Tool action
Soils with good tilth crumble easily in
response to mechanical stress
Tillage tools move soil by applying stresses
that exceed soil strength
Tensile stress
Compression stress
Shear stress
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Granular crumb structure
Compacted massive structure
Soil Texture
Soil Structure
Soil Moisture
Plant Residues
4 main factors affect tilth
http//www.grdc.com.au/growers/gc/gc48/conference1
.htm
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Crop residues Cover Crops Animal manure
Crop residues
20 years of similar tillage intensity but
contrasting levels of organic inputs
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Soil from a long term experiment in Beltsville, MD
20 yrs sod, 5 yrs CT corn
25 yrs CT corn
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Relatively small differences in SOC
Large differences in soil function
After adding water
1.4 C
140 bu/a
1.0 C
48 bu/a
(Visual and comment)
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Small increases in OM can improve
macro-aggregation
Superior air/water relationships
Healthier root growth and function
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How often do you look at crop roots ?
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Feed the soil vs. Feed the crop ?
Both strategies are important !
Healthy roots need available nutrients !
Unhealthy roots use nutrients inefficiently
Plants with poorly developed roots tend to have
nutrient deficiency and drought stress symptoms
Acute root disease
Chronic root malfunction
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Understanding root function
H20
Root exudates activate soil microbes
Transpirational stream
H20
Root growth
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PLOW PAN
Compacted layers can severely limit root growth
Sub-soil water and nutrients
Brady and Weil (2002)
Brady and Weil (2002)
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Long term no-till
Intensive tillage
Network of biopores
Plow pan
Ontario Ministry of Ag and Food
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Manage for maximum biological tillage !
Conventional tillage
Conservation tillage
Adapted from Hunt et al. (1986)
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Tillage is a natural process !
The Burrow Book
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Can biology get the job done ?
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Alternating rows of oats and forage radish
Crop row
Crop row
Row Middle
Groff
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Corn planted following ridge tillage
Cereal rye drilled on ridges
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Multi-functional cover crops
Cover Crops
Cover crop
Adapted from Magdoff and Weil (2004)
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The Challenge
Maintaining residues while accomplishing
tillage objectives
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Fortunately, high residue cultivators are
available !
This cultivator will tend to drag surface residues
http//www.hort.cornell.edu/organicfarm/2004galler
y.html
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High residue cultivator
Undercutting sweeps
Coulter
Ken Fager
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Successful Tillage
No more than necessary
the right tools the right soil conditions proper
adjustment proper operation
http//www.classic-combines.com/images/tillage20t
rain20-20rear20quarter20view2.jpg
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A systems approach
Well adapted crop
Nutrient Management
Water Management
Adapted from Bailey and Lazarovits (2003)
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Progressive sustainability
The Sustainability Spiral
http//www.edpsciences.org/articles/agro/pd
f/2002/07/14.pdf?accessok
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Research experience and opportunities
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Organic fractions obtained using classical alkali
extraction methods
s
S
Most evidence indicates that these fractions are
poorly related to soil function
Humic acid
Fulvic acid
Humin
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Many studies have shown that physical fractions
of OM are related to soil function
Sand sized
Silt and clay sized
Particulate OM
Humus
http//www.grdc.com.au/growers/res_summ/pdfs/cso00
029.pdf
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Functional impact of SOM fractions
http//www.grdc.com.au/growers/res_summ/pdfs/cso00
029.pdf
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Location within the soil matrix affects SOM
dynamics
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Free POM
Sensitivity to management
Intra-aggregate POM
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Mineral associated OM
Adapted from Carter (2002)
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Size/stability fractionation
2 new fractionation methods
Air elutriation
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Size/stability fractionation
Slaking
20-250 ?m
250 ?m
Stable macroaggregates and coarse sand/POM
FD
1 hr
Slakeable microaggregates
20-250 ?m
FD
20-250 ?m
250 ?m
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4 fine fractions
1 hr shaking
Slaking
Slakeable
FD
Macro
Micro
FD
12 hrs shaking in SMP
FD
MicroMacro
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Air elutriation
adjustable aperture
100 mesh screen
2 catchments
South Dakota Seed Blower
Particles are sorted with respect to terminal
velocity
http//seedburo.com
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Permanganate oxidizable C a routine test for
active soil C ??
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Texture and C input regime both affect
permanganate oxidizable C (POC)
100 series
medium C inputs
low C inputs
high C inputs
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Fine C loading is inversely related to fine
fraction content
200 series
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MicroMacro C is weakly related to fine fraction
content
200 series
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MicroMacro C is sensitive to C input regime
a
ab
b
200 series
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Low terminal velocity POC is sensitive to
management
a
ab
abc
bcd
cd
d
g MnO4 oxidizable C / kg soil
Only 2 significance groups without fine fraction
as a covariate
200 series
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Opportunities for research at the Allison Organic
Farm
http//www.markseed.com/hybrid20corn.htm
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Crops often obtain more than half of their N from
SOM
Where does the N come from ?
Magdoff and Weil (2003)
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Crop related changes in mineralizable N
No Till
Plow/Disk
Sorghum
Wheat
Soybean
Adapted from Magdoff and Weil (2004)
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Amino sugar N
No response to additional N
http//cropsci.uiuc.edu/classic/2002/Article9/figu
re1.cfm
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Relationship between crop yield and soil test
Response curves do not describe all the variation
in calibration data !
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Weather often regulates crop productivity more
than nutrient input rates in high
productivity systems
Spatial precision does not solve this problem !!
http//www.fertilizer.org/ifa/publicat/PDF/2005_ag
_frankfurt_lammel_slides.pdf
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Management of mineralization
Havlin et al. (1999)
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Nutrient budgets on organic farms
a review of published data
N
P
K
http//www.organic.aber.ac.uk/library/Nutrient20
budgets20on20organic20farms.pdf
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Root growth and function
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Equipment performance
New Farm
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Organic variety trials
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The hidden half can be revealed by
Does WIU have a soil observatory ?
Innovative teaching
http//www.agrifest.com/images/Site20photos/soil
20root20profile20pit.gif
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Any Questions ?